What is tidal energy?

What is hydropower?

For centuries, we have used hydropower to make tasks lighter. As early as the third century BC, people constructed waterwheels driven by hydropower. Ingenious inventors harnessed waterwheels to a range of mechanical installations that helped people pump water, mill flour, press oils, etc. We find references to the merits of waterwheels in all the ancient cultures (Egyptian, Greek, Roman). Through time, people’s ingenuity increased. They built faster moving blades and millraces that delivered the water to the rotors more efficiently, resulting in increased energy production. The infrastructure around these watermills became more complex. In the 19th century, we saw the first hydropower mills that produced electricity.

There are two important types of hydropower, potential energy and kinetic energy. Each type has its own output, application possibilities and techniques. Partners in the Pro-Tide project examine which solution is best suited to our flat landscape. In view of the fact that our region has no great elevation difference and only a moderate tide on the river, we call it a low dynamic area. The research must show if energy production from water is cost-effective.

Most Hydroelectric plants utilise a phenomenon known as “potential energy”. In the form of water flowing (dropping) downwards though turbines. The turbine blades begin to turn and produce mechanical energy. This provides energy to other installation or generators. If one cubic metre (1 m³) of water drops a distance of 1 metre through a turbine it produces 0.0027 kilowatt-hours. An average family uses 3,800 kilowatt-hours (kWh) of electricity per year. In order to produce sufficient energy, there are often a number of turbines installed next to each other. Obviously, the preferred location is where the largest possible volume of water flows down the greatest possible drop. is just doing that!

Flowing water has motion or kinetic energy. This technique is close to windmill technology. The flow of water turns turbine blades and produces electricity. You can find tidal energy plants at a number places. The earliest tidal powered turbine construction dates back to the middle ages in Brittany. That is also where the first and biggest tidal energy plant was built, with twenty-four turbines, each 10 megawatts. Through time, these machines became more ingenious. Thanks to smarter housings that steer the flow in the required direction, the blades start moving quicker. On top of that, there has been rigorous experimentation with blade shape and spacing. This did not only make them more efficient but also safer. Thanks to slow-turning rotors, there are no fish casualties and the impact on flora and fauna is minimal.

In view of the fact that our region has no great elevation difference and only a moderate tide on the river, we call it a low dynamic area. Partners in the Pro-Tide project examine which solution is best suited to our flat landscape.

Which techniques provide the best output? Which locations the most energy? Is it possible to recoup investment costs for these installations?

We are looking into it for you!

Why is tidal power so predictable?

Obviously, tidal effect is a sum of innumerable factors, geography, wind, the Earth’s rotation, etc. Yet the greater part of its explanation is within our universe. The ancient Greeks noticed that the tides live with the rhythm of the Moon. Newton succeeded in explaining the phenomenon mathematically.

If you conveniently disregard the continents,you can propose that the water forms an even skin around the Earth. The gravitational pull of the Moon pulls the water toward it. The globe changes, as if in the shape of a Rugby ball that protrudes more on the side the Moon is facing. The Earth’s surface that is closest to the Moon has “high water” On the riverbanks, we can see it is “flood tide”. Yet, due to the Earth’s rotation, the Moon’s gravitational pull gets weaker at our location. This leads to lower water once again, and eventually “ebb tide”.

The Moon completes a full rotation of the Earth every 29 days, 12 hours, 44 minutes and 28 seconds. When the Sun, Moon and Earth are all in line, the Sun and Moon both have gravitational pull on the Earth. That pulls the water surface higher, becoming what we know as a “spring tide”. Then an exceptional high tidal flow runs up the Scheldt. When the Sun, Moon and Earth form a 90 ° angle, the forces cancel each other out and we call it a neap tide, there is a much smaller tidal difference.

Obviously, the “power” of the rising and dropping water level has a lot of influence on the amount of energy production that is possible at a location. Yet, so-called low dynamic areas have the hidden advantage of predictability. We can flawlessly calculate the amount of energy generation at any time. Sadly, that is not the case with solar and wind energy.

How many families could benefit from tidal power installations?

An average family uses 3,800 kilowatt-hours (kWh) of electricity per year. In order to produce sufficient energy, most Hydroelectric plants have a number of turbines installed next to each other.

There are various types of hydroelectric plants, with different numbers of households they provide electricity for:

RIVER PLANTS (potential energy)

Natural height difference in the landscape provides a powerful flow of water. The hydroelectric station at Niagara Falls is an extreme example, producing 4.9 million kWh.

HYDROELECTRIC DAMS (potential energy)

If a river has too little natural drop for effective energy production, we can give it a hand. Damming the river creates an artificial lakeand holds it in check. One way you can produce energy is by installing a tube with turbines in the dam and allowing the water to flow through them. The Kariba Dam in Zimbabwe holds back the biggest reservoir in the World. Its surface area of 5,400 km² is as big as the provinces Flemish Brabant (2,106 km²) and East Flanders (3,007 km²) together. Annually, the hydroelectric plant generates 6,400 million kilowatt-hours. Quite impressive, when you think that you can drive an electric car ten kilometres on just 1 kWh.

PUMPED STORAGE PLANTS (potential energy)

This hydroelectric dam variant is especially common in mountainous regions, such as Switzerland. During low energy use periods, the system utilises the “excess” electricity to pump water to higher elevation storage basins. When there is energy demand, the water flows through turbines to lower elevation collecting basins. Then a new cycle starts again. We can even find examples in Belgium as well. The Coo-Trois-Ponts (Luik) is the most important pumped storage plant in Belgium. During periods with low energy use, the pumps utilise “excess” electricity from nuclear plants to move water to higher elevation storage basins.

TIDAL ENERGY PLANTS (kinetic energy – water in motion)

La Rance is the first tidal energy plant in the World, and still one of the biggest. This installation is located in Brittany. The twenty-four 5.4 metre diameter turbines produce over 540 million kWh of electricity annually. According to the operator, the plant produces 90% of Brittany’s electricity.

In August 2011, South Korea opened the largest tidal energy plant in the World. The reservoir was built in 1994, for agricultural purposes but lost its function though industrial pollution. With a 5.6-metre drop, 10 turbines produce
550 GWh of electricity annually.